Risk factors for dysphagia in elderly patients with COPD: a systematic review and meta-analysis protocol

Abstract

Introduction

Given the global trend toward population ageing, chronic obstructive pulmonary disease (COPD) has emerged as an increasingly common health concern. As a chronic pulmonary disorder frequently encountered in clinical settings, COPD typically involves multiple organ-system impairments. Among these impairments, dysphagia is a significant complication in elderly patients with COPD. Dysphagia profoundly compromises the patients’ quality of life and increases risks such as malnutrition and aspiration pneumonia, thereby exacerbating the overall disease burden. Although systematic reviews evaluating dysphagia prevalence in COPD populations, the quantitative synthesis of associated risk factors has been hindered by inadequate reporting in the original studies. At present, no systematic reviews or meta-analyses specifically address the risk factors associated with dysphagia among elderly patients with COPD. Therefore, this systematic review aims to identify and systematically analyse these risk factors, ultimately providing reliable evidence to facilitate early identification and improve clinical management strategies.

Methods and analysis

The literature will be meticulously searched through a variety of electronic databases, including Web of Science, PubMed, Embase, Cochrane Library, China Biomedical Literature Service System (CBM), Chinese Scientific Journal Database (VIP), Wan Fang Database and China National Knowledge Infrastructure (CNKI). We will conduct a thorough investigation of the literature focusing on risk factors associated with dysphagia in elderly individuals diagnosed with COPD, spanning from the inception of each database up to October 2025. Two investigators will independently review the literature, evaluate the quality of studies and extract data based on clearly defined inclusion and exclusion criteria to maintain rigour and consistency. The analysis will employ Stata V.14.0 software for the purposes of data merging and assessment of potential biases. OR along with 95% CI will serve as integrated statistical metrics. Statistical heterogeneity will be assessed using the I² statistic.

Ethics and dissemination

Since this study involves an analysis of previously published literature without direct patient participation, obtaining ethical approval is not required. The outcomes of the current investigation will be disseminated through academic journals following a stringent peer-review process.

PROSPERO registration number

CRD420251006411.

Correspondence to Lingling Weng; [email protected]; Fengqin Cheng; [email protected]

STRENGTHS AND LIMITATIONS OF THIS STUDY

• In reporting this systematic review, we will strictly adhere to the criteria outlined by the Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines.

• No language restrictions will be applied to minimise publication bias.

• Subgroup and sensitivity analyses will be performed to assess heterogeneity and the robustness of results.

• Meta-analysis may not be feasible for some risk factors due to insufficient studies.

Introduction

Chronic obstructive pulmonary disease (COPD), characterised by persistent airflow obstruction and ongoing respiratory symptoms, is a progressive pulmonary condition. COPD has emerged as a significant public health issue globally, currently affecting around 480 million people and resulting in nearly 3 million deaths each year. According to epidemiological forecasts, by 2050, the worldwide COPD prevalence could rise to approximately 600 million cases, making COPD the third leading cause of death globally.^{1 2} Advanced age represents a well-established risk factor for COPD. Epidemiological studies consistently demonstrate a positive correlation between increasing age and disease incidence.^{3 4}

Dysphagia manifests as obstruction, delayed transit of food/liquid or misdirection of food/liquid into the airway during deglutition. Swallowing is a complex physiological process regulated by the central nervous system. It requires precise coordination among multiple anatomical structures, including the oral cavity, pharynx and oesophagus, to facilitate bolus transport. Dysphagia occurs when structural or functional abnormalities develop in these components.^{5 6} Among various risk factors for dysphagia, advanced age represents the most significant independent predictor. Studies indicate that 15–72% of elderly individuals exhibit varying degrees of swallowing impairment, with prevalence demonstrating a marked age-dependent increase.^{7 8} The overall prevalence of swallowing disorders in patients with COPD may reach 32.7%.⁹ However, elderly patients with COPD, due to combined risk factors such as long-term smoking, systemic weakness and inhaled medication use, likely face a higher risk of dysphagia. The prevalence of dysphagia in this population is estimated to exceed 40%.^{10 11} Given accelerated population ageing and the rising prevalence of COPD among elderly populations, swallowing disorders have emerged as a critical public health issue. This issue significantly impacts elderly patients and urgently requires enhanced clinical attention and intervention strategies.

The mechanisms underlying dysphagia in elderly patients with COPD are multifaceted, involving physiological, pathological and neuroregulatory factors. Normally, swallowing is accompanied by a pause in breathing, but in patients with COPD, this coordination often becomes disrupted due to altered breathing patterns.^{12 13} Additionally, age-related physiological changes, such as reduced muscle mass, decreased elasticity of connective tissue, slower swallowing movements, diminished chewing ability, reduced saliva production, oral mucosal atrophy and impaired neural reflexes, directly affect swallowing function.^{14 15} These physiological changes may lead to eating-related fears, potentially resulting in psychological disorders associated with eating. Consequently, reduced food intake may create a vicious cycle involving malnutrition and further swallowing difficulties.¹⁶ Dysphagia also significantly elevates the risk of aspiration and reflux in elderly patients with COPD,¹⁷ potentially triggering acute exacerbation of COPD.¹⁸ This cascade of events increases the risk of hospitalisation, prolongs hospital stays, raises mortality rates and places greater caregiving burdens and financial pressures on patients and their families.^{19 20} Therefore, early identification of risk factors for dysphagia in elderly patients with COPD and targeted interventions are clinically important to reduce dysphagia incidence and improve patient outcomes.

Current evidence regarding risk factors for dysphagia in elderly patients with COPD remains insufficient. The systematic review published by Li et al⁹ in 2021, based on literature up to December 2020, primarily focused on the prevalence of dysphagia among patients with COPD across the lifespan. However, its analysis of risk factors was limited. This limitation may be attributed to the inclusion of only three original studies reporting influencing factors, with significant heterogeneity in reported variables, thereby precluding a meaningful meta-analysis. Furthermore, only one Chinese-language study was included. In recent years, with growing awareness among Chinese clinicians regarding dysphagia in patients with COPD, research in this field has increased significantly. This growth provides more robust data for an in-depth analysis of risk factors. Therefore, this study aims to conduct a systematic review and meta-analysis specifically focused on risk factors for dysphagia in elderly patients with COPD. These findings are expected to yield a comprehensive report that contributes to future exploration in this field.

Methods and analysis

Study design

The protocol for this research was rigorously prepared and carried out in line with the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) Protocols guidelines.²¹ To ensure methodological transparency, the present study has undergone prospective registration in PROSPERO, a recognised international database for systematic reviews (Registration ID: CRD42025100641).

Inclusion and exclusion criteria

Inclusion criteria

Types of participants

The study included patients diagnosed with COPD aged ≥60 years.

Types of studies

• Cross-sectional studies.

• Cohort studies.

• Case–control studies.

Types of content

Studies evaluating one or more risk factors associated with dysphagia in elderly patients with COPD.

Types of outcomes

Clear identification of dysphagia risk factors in older patients with COPD is crucial. Included studies must either explicitly provide OR with 95% CI or provide raw data for their calculation.

Primary outcomes

• Demographic factors: such as age, smoking status, dental condition and similar factors.

• Disease-related factors: such as severity of dyspnoea, comorbidities, COPD severity, oxygen therapy status and dysphagia severity.

• Psychological factors: such as depression and anxiety.

• Other relevant factors: such as self-care ability, feeding posture, frailty status and dietary habits.

Additional outcomes

There are no additional outcomes.

Exclusion criteria

• Research involving patients with COPD who also have comorbidities associated with dysphagia, such as oesophageal cancer and stroke, will be excluded.

• Studies categorised as reviews, systematic reviews or meta-analyses will not be considered.

• Studies with incomplete data will be removed.

• Articles rated as low-quality based on the Newcastle-Ottawa Scale (NOS) or the Agency for Healthcare Research and Quality (AHRQ) assessment tools will also be excluded.

Information sources

Electronic databases

In October 2025, we will search the following databases for literature: PubMed, Web of Science, Cochrane Library, Embase, China National Knowledge Infrastructure (CNKI), Wan Fang Database, Chinese Scientific Journal Database (VIP) and the China Biomedical Literature Service System (CBM). Relevant reviews and studies cited in prior systematic reviews will be hand-searched. A ‘snowball’ search will be conducted using references from included studies to identify additional literature. No language restrictions will be imposed, ensuring comprehensiveness and minimising language-related publication bias. Non-English/non-Chinese literature will be translated using machine translation with manual verification, then included in screening. For disputed content, professional translators or researchers proficient in the respective language will verify the original text. If key information is missing, original authors will be contacted for clarification. If contact cannot be established, the study will be excluded and the reason for exclusion will be documented in the PRISMA flowchart.

Other resources

In addition to searching electronic literature databases, we searched clinical trial registration platforms. These platforms include the WHO’s International Clinical Trials Registry Platform, the Shanghai Evidence-based Nursing Centre and the Chinese Clinical Trial Registry, to identify potentially relevant unpublished or ongoing studies. An illustrative example of our searching approach used in the PROSPERO database is provided in ^{figure 1}.

Figure 1. Search strategy for PROSPERO. MeSH, Medical Subject Headings.

Search strategy

Medical Subject Headings, subheadings and keywords found in the literature study were all factors in developing the search strategy. For other databases, the approach was modified. The preliminary search strategies for PubMed and CNKI were shown in ^{figures 2 and 3}, respectively.

Figure 2. Search strategy for PubMed. COPD, chronic obstructive pulmonary disease; COAD,chronic obstructive airway disease; MeSH, Medical Subject Headings.

Figure 3. Search strategy for China National Knowledge Infrastructure. COPD, chronic obstructive pulmonary disease.

Selection of studies and data extraction

Two researchers trained in evidence-based nursing will independently import all identified articles into EndNote software for screening and verification. Duplicate studies will initially be excluded. Afterward, titles and abstracts will be screened to eliminate irrelevant studies based on predetermined criteria concerning study design, target population and topic. Subsequently, the full texts of the remaining studies will undergo detailed evaluation to determine eligibility according to the inclusion criteria. Data such as the first author’s surname, publication year, study region, research design type, sample population size, diagnostic approach, assessment tools, identified risk factors and corresponding OR with their 95% CI will be methodically extracted after study eligibility assessment. Any discrepancies arising during the selection or extraction phases will be settled by consulting a third reviewer. The complete flowchart of the selection procedure is depicted in ^{figure 4}.

Figure 4. Preferred Reporting Items for Systematic Reviews and Meta-Analyses flowchart of study selection. CBM, China Biomedical Literature Service System; CNKI, China National Knowledge Infrastructure; VIP, Chinese Scientific Journal Database.

Quality evaluation

Two researchers will independently assess the risk of bias in the included studies and cross-check their results. If all assessments are consistent, the final conclusions will be directly confirmed. If discrepancies occur, the specific contentious items and each researcher’s rationale will be clearly documented. The disputed items and relevant study materials will be submitted to a third researcher, who will independently review the evidence provided and arbitrate the disagreements. If disagreements persist, the research team will convene a consensus meeting. The three reviewers will discuss each disputed item in detail, referring to the original scale manual to reach a final unanimous decision. Detailed meeting records will be maintained to ensure transparency.

The evaluation of cross-sectional studies will be conducted using the criteria established by the AHRQ.²² The AHRQ tool comprises 11 items that are evaluated with responses of ‘yes’ (1 point), ‘no’ (0 points) or ‘uncertain’ (0 points). Elevated cumulative scores indicate enhanced methodological rigour, with a peak attainable score of 11. Scores of 0–3 indicate low quality, 4–7 moderate quality and 8–11 high quality. The AHRQ tool’s less stringent criteria facilitate the incorporation of studies that may have methodological limitations but still possess valid data, thus ensuring sufficient sample sizes for analysis.

The quality assessment of the selected cohort and case–control studies will be conducted using the NOS.²³ This evaluation tool scrutinises three methodological areas: participant selection (up to 4 points), group comparability (up to 2 points) and the assessment of exposure or outcomes (up to 3 points), culminating in a maximum score of 9 points. According to this evaluation framework, research will be categorised into three distinct quality levels: high (7–9 points), moderate (5–6 points) and low (0–4 points).

To control for bias, sensitivity analyses will be conducted by excluding low-scoring studies and comparing results across different quality subgroups to assess the potential impact of bias.

Data synthesis and analysis

Stata V.14.0 will be used for meta-analysis. The combined outcomes will be presented as OR with their associated 95% CI. The I² statistic will be used to quantify the heterogeneity among the included studies. When there is minimal heterogeneity (p≥0.1 and I²<50%), the fixed-effects model will be used. On the other hand, a random-effects model will be applied when there is significant heterogeneity (p<0.1 and I²≥50%). The random-effects model may be the best choice even if there is no obvious clinical heterogeneity. Subgroup and sensitivity analyses can provide additional aid in determining potential sources of variability. This analysis will be limited to a narrative summary if it is unable to clarify the origins of heterogeneity.

Sensitivity analysis will use the leave-one-out method. Each study will be excluded individually to recalculate the pooled effect size, evaluating the influence of individual studies on the overall results. Studies will be grouped based on specific characteristics, and effect size differences across subgroups will be compared.

The presence of publication bias will be visually evaluated using funnel plot analyses. Egger’s statistical test will be conducted to quantitatively assess funnel plot symmetry; a result of p>0.05 will imply a symmetrical distribution, thereby suggesting the absence of publication bias. The significance level α will be set at 0.05.

Certainty of the evidence

We will employ the Grading of Recommendations Assessment, Development and Evaluation(GRADE) tool to evaluate the quality of evidence for all outcome measures included in the meta-analysis. Two independent reviewers trained in the GRADE methodology will conduct the assessments, and any disagreements will be resolved by a third reviewer. The evaluation will systematically examine five critical domains: study limitations (risk of bias), consistency of findings, indirectness of evidence, precision of effect estimates and potential publication bias. The evidence level will be graded as high, moderate, low or very low.²⁴ Each domain will be rigorously assessed according to the GRADE guidelines, with the overall evidence rating determined through a comprehensive synthesis of these elements.

Time frame for study completion

Expected research timeline (^{table 1}).

Table 1

Expected research timeline

Stage	Start time	Completion time
Search strategy formulation	√	√
Formal retrieval	October 2025	November 2025
Literature screening	November 2025	December 2025
Quality assessment	December 2025	January 2026
Data extraction	March 2026	April 2026
Data synthesis	April 2026	May 2026
Data analysis	May 2026	July 2026

Discussion

This study aims to integrate existing research data through a systematic review and meta-analysis, providing more comprehensive and reliable evidence-based support for clinical practice. Compared with individual studies, this research applies rigorous criteria for literature screening and quality assessment, thus enhancing statistical power through quantitative synthesis and making the findings more compelling. The anticipated conclusions will offer a scientific basis for clinicians to early identify elderly patients with COPD at high risk of dysphagia early. Additionally, potential sources of heterogeneity will be explored through subgroup and sensitivity analyses to strengthen the stability and clinical applicability of the results. These findings may serve as a reference for optimising existing clinical pathways and promoting multidisciplinary collaborative management of swallowing function in elderly patients with COPD.

Amendments

If any modifications are made to this protocol, they will be recorded on PROSPERO.

Ethics and dissemination

Not applicable. The results will be disseminated in a peer-reviewed journal.

Footnote

Contributors All authors contributed to the development of the proposal and the writing of the manuscript. TZ, LW and FC defined the research questions. TZ, MY and LW wrote the initial draft of the manuscript. FC revised the initial draft. All authors reviewed the manuscript and agreed on the final version. Guarantor is LW.

Funding This work is supported by Southwest Medical University—Key Research Base for Humanities and Social Sciences of the Sichuan Provincial Department of Education—Sichuan Hospital Management and Development Research Center project (project number SCYG2024-23). Sichuan Medical Association Wound/Chronic Disease (Taige) Special Research Project (project number 2024TG42). North Sichuan Medical College—Sichuan Provincial Research Center for the Development of Grassroots Health Services Project (project number SWFZ24-Y-29).

Competing interests None declared.

Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

Provenance and peer review Not commissioned; externally peer reviewed.

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